System suitable for the hydrocyanation of olefinically unsaturated compounds

ABSTRACT

A system which is suitable as a catalyst for the hydrocyanation of olefinically unsaturated compounds and comprises
     a) Ni(0)   b) a compound which complexes Ni(0) as a ligand and contains trivalent phosphorus,   c) a Lewis acid
 
and
   d) a compound of the formula M R n  
 
where
   M: Al or Ti   R: identical or different monovalent alkoxy radicals, in which case a plurality of alkoxy radicals may be bonded together, and additionally, in the case that M=Al, R may be identical or different monovalent alkyl radicals, in which case a plurality of alkyl radicals may be bonded together or one or more alkyl radicals may be bonded to one or more of the abovementioned alkoxy radicals,   n: valency of M,
 
and processes for hydrocyanating an olefinically unsaturated compound in the presence of such a system.

This application claims priority from PCT Application No.PCT/EP2004/003103 filed Mar. 24, 2004 and German Application Ser. No.10314761.6 filed Mar. 31, 2003, the disclosures of each application areincorporated herein by reference.

The present invention relates to a system which is suitable as acatalyst for the hydrocyanation of olefinically unsaturated compoundsand comprises

-   a) Ni(0)-   b) a compound which complexes Ni(0) as a ligand and contains    trivalent phosphorus,-   c) a Lewis acid    and-   d) a compound of the formula M R_(n)    where-   M: Al or Ti-   R: identical or different monovalent alkoxy radicals, in which case    a plurality of alkoxy radicals may be bonded together, and    additionally, in the case that M=Al, R may be identical or different    monovalent alkyl radicals, in which case a plurality of alkyl    radicals may be bonded together or one or more alkyl radicals may be    bonded to one or more of the abovementioned alkoxy radicals,-   n: valency of M.

In addition, it relates to a process for hydrocyanating an olefinicallyunsaturated compound in the presence of such a system.

Processes for hydrocyanating an olefinically unsaturated nitrile, inparticular the preparation of adipodinitrile by hydrocyanating anolefinically unsaturated compound such as 2-cis-pentenenitrile,2-trans-pentenenitrile, 3-cis-pentenenitrile, 3-trans-pentenenitrile,4-pentenenitrile, E-2-methyl-2-butenenitrile,Z-2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile or mixturesthereof, in the presence of a catalyst system comprising a Lewis acidand a complex containing a phosphorus compound suitable as a ligand,such as a monodentate, preferably multidentate, in particular bidentate,compound which coordinates to a central atom via a phosphorus atom whichmay be present as a phosphine, phosphite, phosphonite or phosphinite ormixture thereof, and a central atom, preferably nickel, cobalt orpalladium, in particular nickel, more preferably in the form of nickel(0), are known, for example from U.S. Pat. No. 3,496,217, U.S. Pat. No.3,496,218, U.S. Pat. No. 4,705,881, U.S. Pat. No. 4,774,353, U.S. Pat.No. 4,874,884, U.S. Pat. No. 5,773,637, U.S. Pat. No. 6,127,567, U.S.Pat. No. 6,171,996 B1 and U.S. Pat. No. 6,380,421 B1.

It is an object of the present invention to provide a system which issuitable as a catalyst for the hydrocyanation of olefinicallyunsaturated compounds and exhibits an improved space-time yield ofhydrocyanation products compared to the known systems.

We have found that this object is achieved by the system defined at theoutset and by a process for hydrocyanating an olefinically unsaturatedcompound in the presence of such a system.

The preparation of Ni(0)-containing catalyst systems is known per seand, for the purposes of the present invention, can be effected byprocesses known per se.

The system also additionally comprises a compound which is suitable as aligand for Ni(0) and contains at least one trivalent phosphorus atom, ora mixture of such compounds.

In a preferred embodiment, the compound used as a ligand may be one ofthe formulaP(X¹R¹)(X²R²)(X³R³)  (I).

In the context of the present invention, this compound is a singlecompound or a mixture of different compounds of the aforementionedformula.

X¹, X², X³ may each independently be oxygen or a single bond.

When all of the X¹, X² and X³ groups are single bonds, compound (I) is aphosphine of the formula P(R¹ R² R³) with the definitions of R¹, R² andR³ specified in this description.

When two of the X¹, X² and X³ groups are single bonds and one is oxygen,compound (I) is a phosphinite of the formula P(OR¹)(R²)(R³) orP(R¹)(OR²)(R³) or P(R¹)(R²)(OR³) with the definitions of R¹, R² and R³specified in this description.

When one of the X¹, X² and X³ groups is a single bond and two areoxygen, compound (I) is a phosphonite of the formula P(OR¹)(OR²)(R³) orP(R¹)(OR²)(OR³) or P(OR¹)(R²)(OR³) with the definitions of R¹, R² and R³specified in this description.

In a preferred embodiment, all of the X¹, X² and X³ groups should beoxygen, so that compound (I) is advantageously a phosphite of theformula P(OR¹)(OR²)(OR³) with the definitions of R¹, R² and R³ specifiedin this description.

According to the invention, R¹, R², R³ are each independently identicalor different organic radicals.

R¹, R² and R³ are each independently alkyl radicals, advantageouslyhaving from 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl,i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, aryl groups such asphenyl, o-tolyl, m-tolyl, p-tolyl, 1-naphthyl, 2-naphthyl, orhydrocarbyl, advantageously having from 1 to 20 carbon atoms, such as1,1′-biphenol, 1,1′-binaphthol.

The R¹, R² and R³ groups may be bonded together directly, i.e. notsolely via the central phosphorus atom. Preference is given to the R¹,R² and R³ groups not being bonded together directly.

In a preferred embodiment, the R¹, R² and R³ groups are radicalsselected from the group consisting of phenyl, o-tolyl, m-tolyl andp-tolyl.

In a particularly preferred embodiment, a maximum of two of the R¹, R²and R³ groups should be phenyl groups.

In another preferred embodiment, a maximum of two of the R¹, R² and R³groups should be o-tolyl groups.

Particularly preferred compounds which may be used are those of theformula(o-tolyl-O—)_(w)(m-tolyl-O—)_(x)(p-tolyl-O—)_(y)(phenyl-O—)_(z)Pwhere w, x, y, z are each a natural number

-   -   where w+x+y+z=3 and        -   w, z are each less than or equal to 2,            such as (p-tolyl-O—)(phenyl)₂P, (m-tolyl-O—)(phenyl)₂P,            (o-tolyl-O—)(phenyl)₂P, (p-tolyl-O—)₂(phenyl)P,            (m-tolyl-O—)₂(phenyl)P, (o-tolyl-O—)₂(phenyl)P,            (m-tolyl-O—)(p-tolyl-O—)(phenyl)P,            (o-tolyl-O—)(p-tolyl-O—)(phenyl)P, (o-tolyl-O—)            (m-tolyl-O—)(phenyl)P, (p-tolyl-O—)₃P,            (m-tolyl-O—)(p-tolyl-O—)₂P, (o-tolyl-O—)(p-tolyl-O—)₂P,            (m-tolyl-O—)₂(p-tolyl-O—)P, (o-tolyl-O—)₂(p-tolyl-O—)P,            (o-tolyl-O—)(m-tolyl-O—) (p-tolyl-O—)P, (m-tolyl-O—)₃P,            (o-tolyl-O—)(m-tolyl-O—)₂P, (o-tolyl-O—)₂(m-tolyl-O—)P or            mixtures of such compounds.

For example, mixtures comprising (m-tolyl-O—)₃P,(m-tolyl-O—)₂(p-tolyl-O—)P, (m-tolyl-O—)(p-tolyl-O—)₂P and(p-tolyl-O—)₃P may be obtained by reacting a mixture comprising m-cresoland p-cresol, in particular in a molar ratio of 2:1, as obtained in thedistillative workup of crude oil, with a phosphorus trihalide, such asphosphorus trichloride.

Such compounds and their preparation are known per se.

In a further preferred embodiment, the compound suitable as a ligand forNi(0) which is used may be one of the formula

where

-   X¹¹, x¹², x¹³, x²¹, X²², X²³ are each independently oxygen or a    single bond,-   R¹¹, R¹² are each independently identical or different, individual    or bridged organic radicals-   R²¹, R²² are each independently identical or different, individual    or bridged organic radicals,-   Y is a bridging group.

In the context of the present invention, such a compound is a singlecompound or a mixture of different compounds of the aforementionedformula.

In a preferred embodiment, X¹¹, X¹², X¹³, X²¹, X²², X²³ may each beoxygen. In such a case, the bridging group Y is bonded to phosphitegroups.

In another preferred embodiment, X¹¹ and X¹² may each be oxygen and X¹³a single bond, or X¹¹ and X¹³ oxygen and X¹² a single bond, so that thephosphorus atom surrounded by X¹¹, X¹² and X¹³ is the central atom of aphosphonite. In such a case, X²¹, X²² and X²³ may be oxygen, or X²¹ andX²² may each be oxygen and X²³ a single bond, or X²¹ and X²³ may each beoxygen and X²² a single bond, or X²³ may be oxygen and X²¹ and X²² eacha single bond, or X²¹ may be oxygen and X²² and X²³ each a single bond,or X²¹, X²² and X²³ may each be a single bond, so that the phosphorusatom surrounded by X²¹, X²² and X²³ may be the central atom of aphosphite, phosphonite, phosphinite or phosphine, preferably aphosphonite.

In another preferred embodiment, X¹³ may be oxygen and X¹¹ and X¹² eacha single bond, or X¹¹ may be oxygen and X¹² and X¹³ each a single bond,so that the phosphorus atom surrounded by X¹¹, X¹² and X¹³ is thecentral atom of a phosphinite. In such a case, X²¹, X²² and X²³ may eachbe oxygen, or X²³ may be oxygen and X²¹ and X²² a single bond, or X²¹may be oxygen and X²² and X²³ each a single bond, or X²¹, X²² and X²³may each be a single bond, so that the phosphorus atom surrounded byX²¹, X²² and X²³ may be the central atom of a phosphite, phosphinite orphosphine, preferably a phosphinite.

In another preferred embodiment, X¹¹, X¹² and X¹³ may each be a singlebond, so that the phosphorus atom surrounded by X¹¹, X¹² and X¹³ is thecentral atom of a phosphine. In such a case, X²¹, X²² and X²³ may eachbe oxygen, or X²¹, X²² and X²³ may each be a single bond, so that thephosphorus atom surrounded by X²¹, X²² and X²³ may be the central atomof a phosphite or phosphine, preferably a phosphine.

The bridging group Y is advantageously an aryl group which issubstituted, for example by C₁-C₄-alkyl, halogen, such as fluorine,chlorine, bromine, halogenated alkyl, such as trifluoromethyl, aryl,such as phenyl, or is unsubstituted, preferably a group having from 6 to20 carbon atoms in the aromatic system, in particular pyrocatechol,bis(phenol) or bis(naphthol).

The R¹¹ and R¹² radicals may each independently be the same or differentorganic radicals. Advantageous R¹¹ and R¹² radicals are aryl radicals,preferably those having from 6 to 10 carbon atoms, which may beunsubstituted or mono- or polysubstituted, in particular by C₁-C₄-alkyl,halogen, such as fluorine, chlorine, bromine, halogenated alkyl, such astrifluoromethyl, aryl, such as phenyl, or unsubstituted aryl groups.

The R²¹ and R²² radicals may each independently be the same or differentorganic radicals. Advantageous R²¹ and R²² radicals are aryl radicals,preferably those having from 6 to 10 carbon atoms, which may beunsubstituted or mono- or polysubstituted, in particular by C₁-C₄-alkyl,halogen, such as fluorine, chlorine, bromine, halogenated alkyl, such astrifluoromethyl, aryl, such as phenyl, or unsubstituted aryl groups.

The R¹¹ and R¹² radicals may each be separate or bridged.

The R²¹ and R²² radicals may each be separate or bridged.

The R¹¹, R¹², R²¹ and R²² radicals may each be separate, two may bebridged and two separate, or all four may be bridged, in the mannerdescribed.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV and V specified in U.S. Pat. No. 5,723,641.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV, V, VI and VII specified in U.S. Pat. No.5,512,696, in particular the compounds used there in examples 1 to 31.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIVand XV specified in U.S. Pat. No. 5,821,378, in particular the compoundsused there in examples 1 to 73.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV, V and VI specified in U.S. Pat. No.5,512,695, in particular the compounds used there in examples 1 to 6.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII andXIV specified in U.S. Pat. No. 5,981,772, in particular the compoundsused there in examples 1 to 66.

In a particularly preferred embodiment, useful compounds are thosespecified in U.S. Pat. No. 6,127,567 and the compounds used there inexamples 1 to 29.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, III, IV, V, VI, VII, VIII, IX and X specified in U.S.Pat. No. 6,020,516, in particular the compounds used there in examples 1to 33.

In a particularly preferred embodiment, useful compounds are thosespecified in U.S. Pat. No. 5,959,135, and the compounds used there inexamples 1 to 13.

In a particularly preferred embodiment, useful compounds are those ofthe formula I, II, and III specified in U.S. Pat. No. 5,847,191.

In a particularly preferred embodiment, useful compounds are thosespecified in U.S. Pat. No. 5,523,453, in particular the compoundsillustrated there in formula 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20 and 21.

In a particularly preferred embodiment, useful compounds are thosespecified in WO 01/14392, preferably the compounds illustrated there informula V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XXI,XXII, XXIII.

In a particularly preferred embodiment, useful compounds are thosespecified in WO 98/27054.

In a particularly preferred embodiment, useful compounds are thosespecified in WO 99/13983.

In a particularly preferred embodiment, useful compounds are thosespecified in WO 99/64155.

In a particularly preferred embodiment, useful compounds are thosespecified in the German laid-open specification DE 10038037.

In a particularly preferred embodiment, useful compounds are thosespecified in the German laid-open specification DE 10046025.

Such compounds and their preparation are known per se.

In a further preferred embodiment, a mixture of one or more of theaforementioned compounds which are suitable as a ligand for Ni(0) andcontain one phosphorus atom, and one or more compounds which aresuitable as a ligand for Ni(0) and contain two phosphorus atoms may beused.

In this case, the ratio of the first component to the second componentmay be in the range from 4/1 to 1/1 mol/mol.

In a particularly preferred embodiment, useful systems are those whichare specified in the international patent application PCT/EP02/07888 andcomprise Ni(0) and such mixtures.

In addition, the system comprises a Lewis acid.

In the context of the present invention, a Lewis acid is either a singleLewis acid or else a mixture of a plurality of, for example two, threeor four, Lewis acids.

Useful Lewis acids are inorganic or organic metal compounds in which thecation is selected from the group consisting of scandium, titanium,vanadium, chromium, manganese, iron, cobalt, copper, zinc, boron,aluminum, yttrium, zirconium, niobium, molybdenum, cadmium, rhenium andtin. Examples include ZnBr₂, ZnI₂, ZnCl₂, ZnSO₄, CuCl₂, CuCl,Cu(O₃SCF₃)₂, CoCl₂, Col₂, FeI₂, FeCl₃, FeCl₂, FeCl₂(THF)₂, TiCl₄(THF)₂,TiCl₄, TiCl₃, ClTi(O-i-propyl)₃, MnCl₂, ScCl₃, AlCl₃, (C₈H₁₇)AlCl₂,(C₈H₁₇)₂AlCl, (i-C₄H₉)₂AlCl, (C₆H₅)₂AlCl, (C₆H₅)AlCl₂, ReCl₅, ZrCl₄,NbCl₅, VCl₃, CrCl₂, MoCl₅, YCl₃, CdCl₂, LaCl₃, Er(O₃SCF₃)₃, Yb(O₂CCF₃)₃,SmCl₃, B(C₆H₅)₃, TaCl₅, as described, for example, in U.S. Pat. No.6,127,567, U.S. Pat. No. 6,171,996 and U.S. Pat. No. 6,380,421. Alsouseful are metal salts such as ZnCl₂, CoI₂ and SnCl₂, and organometalliccompounds such as RAlCl₂, R₂AlCl, RSnO₃SCF₃ and R₃B, where R is an alkylor aryl group, as described, for example, in U.S. Pat. No. 3,496,217,U.S. Pat. No. 3,496,218 and U.S. Pat. No. 4,774,353. According to U.S.Pat. No. 3,773,809, the promoter used may also be a metal in cationicform which is selected from the group consisting of zinc, cadmium,beryllium, aluminum, gallium, indium, thallium, titanium, zirconium,hafnium, erbium, germanium, tin, vanadium, niobium, scandium, chromium,molybdenum, tungsten, manganese, rhenium, palladium, thorium, iron andcobalt, preferably zinc, cadmium, titanium, tin, chromium, iron,aluminium and cobalt, and the anionic moiety of the compound may beselected from the group consisting of halides such as fluoride,chloride, bromide and iodide, anions of lower fatty acids having from 2to 7 carbon atoms, HPO₃ ²⁻, H₃PO²⁻, CF₃COO⁻, C₇H₁₅OSO₂ ⁻ or SO₄ ²⁻.Further suitable promoters disclosed by U.S. Pat. No. 3,773,809 areborohydrides, organoborohydrides and boric esters of the formula R₃B andB(OR)₃, where R is selected from the group consisting of hydrogen, arylradicals having from 6 to 18 carbon atoms, aryl radicals substituted byalkyl groups having from 1 to 7 carbon atoms and aryl radicalssubstituted by cyano-substituted alkyl groups having from 1 to 7 carbonatoms, advantageously triphenylboron. Moreover, as described in U.S.Pat. No. 4,874,884, it is possible to use synergistically activecombinations of Lewis acids, in order to increase the activity of thecatalyst system. Suitable promoters may, for example, be selected fromthe group consisting of CdCl₂, FeCl₂, ZnCl₂, B(C₆H₅)₃ and (C₆H₅)₃SnX,where X=CF₃SO₃, CH₃C₆H₄SO₃ or (C₆H₅)₃BCN, and the preferred ratiospecified of promoter to nickel is from about 1:16 to about 50:1.

In the context of the present invention, the term Lewis acid alsoincludes the promoters specified in U.S. Pat. No. 3,496,217, U.S. Pat.No. 3,496,218, U.S. Pat. No. 4,774,353, U.S. Pat. No. 4,874,884, U.S.Pat. No. 6,127,567, U.S. Pat. No. 6,171,996 and U.S. Pat. No. 6,380,421.

Particularly preferred Lewis acids among those mentioned are inparticular metal salts, more preferably metal halides, such asfluorides, chlorides, bromides, iodides, in particular chlorides, ofwhich particular preference is given to zinc chloride, iron(II) chlorideand iron(III) chloride.

According to the invention, the system comprises a compound d) of theformula M R_(n)

where

-   M: Al or Ti-   R: identical or different monovalent alkoxy radicals, in which case    a plurality of alkoxy radicals may be bonded together, and    additionally, in the case that M=Al, R may be identical or different    monovalent alkyl radicals, in which case a plurality of alkyl    radicals may be bonded together or one or more alkyl radicals may be    bonded to one or more of the abovementioned alkoxy radicals,-   n: valency of M.

In the context of the present invention, a compound d) may be a singlecompound or else a mixture of different compounds of this type, and thedifferent compounds may differ in the nature of M, the nature of R orboth.

According to the invention, M is aluminum or titanium, and the valency nof aluminum in compound d) should advantageously be three and thevalency n of titanium in compound d) should advantageously be three orfour, in particular four. In the context of the definition of n, thevalency refers to the number of R radicals on M, irrespective of theoxidation number of M which can be calculated for the particularstructure M R_(n) in compound d).

In the case that M is titanium, R is identical or different, preferablyidentical, monovalent alkoxy radicals, in which case a plurality ofalkoxy radicals may be bonded together, preferably C₁-C₄-alkoxyradicals, such as methoxy, ethoxy, 1-propoxy, 2-propoxy, 1-n-butoxy,2-n-butoxy, 1-isobutoxy or 2-isobutoxy, preferably Ti(OMe)₄, Ti(OEt)₄,Ti(O-i-Pr)₄, Ti(O-n-Pr)₄, in particular Ti(O-i-Pr)₄.

In a preferred embodiment, compound d) may be a titanium tetraalkoxide,in particular Ti(O-i-Pr)₄.

In the case that M is aluminum, R is identical or different, preferablyidentical, monovalent alkoxy radicals, in which case a plurality ofalkoxy radicals may be bonded together, preferably C₁-C₄-alkoxyradicals, such as methoxy, ethoxy, 1-propoxy, 2-propoxy, 1-n-butoxy,2-n-butoxy, 1-isobutoxy or 2-isobutoxy, preferably Al(OMe)₃, Al(OEt)₃,Al(O-i-Pr)₃, Al(O-s-Bu)₃, in particular Al(O-s-Bu)₃ or identical ordifferent, preferably identical, monovalent alkyl radicals, in whichcase a plurality of alkyl radicals may be bonded together or one or morealkyl radicals may be bonded to one or more of the abovementioned alkoxyradicals, preferably C₁-C₄-alkyl radicals such as methyl, ethyl,1-propyl, 2-propyl, 1-n-butyl, 2-n-butyl, 1-isobutyl or 2-isobutyl,preferably Me₃Al, Et₃Al, i-Pr₃Al, Bu₃Al, in particular Et₃Al, or suchmixed alkoxyalkyl radicals.

In a preferred embodiment, compound d) may be an aluminum trialkoxide,in particular Al(O-s-Bu)₃.

In a further preferred embodiment, compound d) may be atrialkylaluminum, in particular Et₃Al.

Advantageously, compound d), based on Ni, may be used in amounts of from0.01 to 2, preferably from 0.01 to 1.5, in particular from 0.01 to 1mol/mol (w/w).

The preparation of catalyst systems comprising the components a), b) andc) is known per se; the system according to the invention can beprepared in accordance with these known processes.

In processes for hydrocyanating olefinically unsaturated compounds inthe presence of Ni(0)-containing catalyst systems, it is advantageous inaccordance with the invention to use the present systems comprisingcompounds a), b), c) and d) as Ni(0)-containing catalysts.

In the context of the present invention, olefinically unsaturatedcompound refers either to a single olefinically unsaturated compound orto a mixture of such olefinically unsaturated compounds.

Useful olefinically unsaturated compounds are compounds which have oneor more, such as two, three or four, preferably one or two, inparticular one, carbon-carbon double bonds. The olefinically unsaturatedcompounds may advantageously be a branched or unbranched alkene,preferably having from 2 to 10 carbon atoms, or an arylalkene, such as amonoarylalkene or bisarylalkene, preferably having from 2 to 10 carbonatoms in the alkene backbone.

Such olefinically unsaturated compounds may be unsubstituted.

In a preferred embodiment, a substituted olefinically unsaturatedcompound is used, preferably an olefinically unsaturated compound whichcontains a functional group selected from the group consisting of —CN,—COOR³¹, —CONR³²R³³

where R³¹, R³², R³³: each independently, in the case that R³² and R³³are the same or different, H or alkyl, preferably C₁-C₄-alkyl, such asmethyl, ethyl, 1-propyl, 2-propyl, 1-n-butyl, 2-n-butyl, 1-isobutyl or2-isobutyl.

In a further preferred embodiment, the substituted olefinicallyunsaturated compound used may be a compound of the formula (C₄H₇)-X

where X: functional group selected from the group consisting of —CN,—COOR⁴¹, —CONR⁴²R⁴³

where R⁴¹, R⁴², R⁴³: each independently, in the case that R⁴² and R⁴³are the same or different, H or alkyl, preferably C₁-C₄-alkyl, such asmethyl, ethyl, 1-propyl, 2-propyl, 1-n-butyl, 2-n-butyl, 1-isobutyl or2-isobutyl.

In a further preferred embodiment, the olefinically unsaturated compoundused may be a branched, preferably linear, pentenenitrile, such as2-cis-pentenenitrile, 2-trans-pentenenitrile, 3-cis-pentenenitrile,3-trans-pentenenitrile, 4-pentenenitrile, E-2-methyl-2-butenenitrile,Z-2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile or mixturesthereof.

In a particularly preferred embodiment, the olefinically unsaturatedcompound used is 3-pentenenitrile, such as 3-cis-pentenenitrile or3-trans-pentenenitrile, 4-pentenenitrile or mixtures thereof.

Such pentenenitriles can be obtained by processes known per se, forexample by hydrocyanation of butadiene in the presnce ofNi(0)-containing catalysts.

Processes for hydrocyanating olefinically unsaturated compounds in thepresence of Ni(0)-containing catalyst systems are known per se. Theprocesses according to the invention can be carried out in accordancewith these processes known per se.

The adiponitrile (“ADN”) obtainable as a product in such ahydrocyanation or the compounds obtainable by hydrogenating ADN,6-aminocapronitrile (“ACN”) and hexamethylenediamine (“HMD”) can be usedto prepare polyamides, in particular nylon-6 and nylon-6,6.

The invention is illustrated by the nonlimiting examples which follow.

EXAMPLES

All examples and comparative examples were carried out in an argonprotective gas atmosphere.

Nickel(0)(m-/p-tolyl phosphite)₅₋₇ (“NTP”) is a solution of 2.35% byweight of nickel(0) with 19% by weight of 3-pentenenitrile (“3PN”) and78.65% by weight of m-/p-tolyl phosphite with an m/p ratio of 2:1.

The ligands used were:

In addition, “ADN” means adiponitrile, “4PN” means 4-pentenenitrile and“Ni(COD)₂” means Ni(0)-bis(cyclooctadiene) complex.

Hydrocyanation of 3PN to ADN

Example 1 (Comparative), (0.42 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. In an Ar carrier gasstream, 277 eq. of HCN/h*Ni were then injected. After 10 min., themixture took up no more HCN; a sample was taken from the reactionmixture and the following results were obtained by gas chromatography(GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 5.0 0.1 1.2 94.0

Example 2 (Comparative) (0.42 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 1 eq. of Et₃Al wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 276 eq. of HCN/h*Ni were then injected. After 20min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 4.8 0.1 0.9 88.0

Example 3 (Comparative) (0.42 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 351 eq. of HCN/h*Ni were then injected. After 65min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 2.1 2.0 35.8 94.8

Example 4 (Inventive) (0.47 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of Et₃Al and 1eq. of ZnCl₂ was added to this mixture and it was stirred for a further5 min. In an Ar carrier gas stream, 303 eq. of HCN/h*Ni were theninjected. After 140 min., the mixture took up no more HCN; a sample wastaken from the reaction mixture and the following results were obtainedby gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 0.9 3.1 64.0 95.5

Example 5 (Comparative): (0.47 mmol of Ni(0))

1 eq. of Ni(COD)₂ was admixed with 3 eq. of ligand 1 and 1000 eq. of3PN, stirred at 25° C. for one hour and heated to 73° C. 1 eq. of ZnCl₂was added to this mixture and it was stirred for a further 5 min. In anAr carrier gas stream, 271 eq. of HCN/h*Ni were then injected. After 120min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 1.7 3.3 50.9 94.0

Example 6 (Inventive) (0.47 mmol of Ni(0))

1 eq. of Ni(COD)₂ was admixed with 3 eq. of ligand 1 and 1000 eq. of3PN, stirred at 25° C. for one hour and heated to 73° C. 1 eq. of Et₃Aland 1 eq. of ZnCl₂ was added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 268 eq. of HCN/h*Ni werethen injected. After 150 min., the mixture took up no more HCN; a samplewas taken from the reaction mixture and the following results wereobtained by gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 1.4 3.4 61.3 94.7

Example 7 (Comparative): (0.38 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 1 eq. of FeCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 319 eq. of HCN/h*Ni were then injected. After 60min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 2.5 2.5 31.8 92.6

Example 8 (Inventive) (0.38 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 0.35 eq. of Et₃Aland 1 eq. of FeCl₂ was added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 324 eq. of HCN/h*Ni werethen injected. After 110 min., the mixture took up no more HCN; a samplewas taken from the reaction mixture and the following results wereobtained by gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 1.5 3.5 50.9 93.5

Example 9 (Comparative) (0.46 mmol of Ni(0))

1 eq. of Ni(COD)₂ was admixed with 3 eq. of ligand 1 and 1000 eq. of3PN, stirred at 25° C. for one hour and heated to 73° C. 1 eq. of FeCl₂was added to this mixture and it was stirred for a further 5 min. In anAr carrier gas stream, 256 eq. of HCN/h*Ni were then injected. After 140min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 1.3 3.9 61.1 94.0

Example 10 (Inventive) (0.4 mmol of Ni(0))

1 eq. of Ni(COD)₂ was admixed with 3 eq. of ligand 1 and 1000 eq. of3PN, stirred at 25° C. for one hour and heated to 73° C. 0.35 eq. ofEt₃Al and 1 eq. of FeCl₂ was added to this mixture and it was stirredfor a further 5 min. In an Ar carrier gas stream, 300 eq. of HCN/h*Niwere then injected. After 150 min., the mixture took up no more HCN; asample was taken from the reaction mixture and the following resultswere obtained by gas chromatography (GC percent by weight, internalstandard: ethylbenzene):

4PN MGN AND ADN selectivity (%) 1.0 4.2 69.4 94.3

Example 11 (Comparative) (0.43 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 10 eq. ofAl(O-s-Bu)₃ and 1 eq. of FeCl₂ was added to this mixture and it wasstirred for a further 5 min. In an Ar carrier gas stream, 294 eq. ofHCN/h*Ni were then injected. After 15 min., the mixture took up no moreHCN; a sample was taken from the reaction mixture and the followingresults were obtained by gas chromatography (GC percent by weight,internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 1.6 0.1 0.2 —

Example 12 (Inventive) (0.42 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 0.5 eq. ofAl(O-s-Bu)₃ and 1 eq. of ZnCl₂ was added to this mixture and it wasstirred for a further 5 min. In an Ar carrier gas stream, 361 eq. ofHCN/h*Ni were then injected. After 80 min., the mixture took up no moreHCN; a sample was taken from the reaction mixture and the followingresults were obtained by gas chromatography (GC percent by weight,internal standard: ethylbenzene):

4PN MGN AND ADN selectivity (%) 1.8 3.7 51.9 93.4

Example 13 (Inventive) (0.42 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 73° C. 1 eq. of Ti(O-Bu)₄and 1 eq. of ZnCl₂ was added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 296 eq. of HCN/h*Ni werethen injected. After 100 min., the mixture took up no more HCN; a samplewas taken from the reaction mixture and the following results wereobtained by gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 2.1 3.2 48.6 93.8

Example 14 (Comparative): (0.3 mmol of Ni(0))

1 eq. of NTP was admixed with 300 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 260 eq. of HCN/h*Ni were then injected. After 1, 2,3, 4, 5 and 10 minutes, a sample was taken from the reaction mixture andthe following results were obtained by gas chromatography (GC percent byweight, internal standard: ethylbenzene):

Min 4PN ADN 1 2.6 3.7 2 3.0 7.1 3 3.3 9.8 4 3.3 12.1 5 3.1 15.5 10 2.627.2

Example 15a (Inventive) (0.3 mmol of Ni(0))

1 eq. of NTP was admixed with 300 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of Et₃Al and 1eq. of ZnCl₂ was added to this mixture and it was stirred for a further5 min. In an Ar carrier gas stream, 260 eq. of HCN/h*Ni were theninjected. After 1, 2, 3, 4, 5 and 10 minutes, a sample was taken fromthe reaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

Min 4PN ADN 1 1.9 3.6 2 2.2 4.5 3 2.4 7.7 4 2.6 10.9 5 2.6 11.5 10 1.525.4

Example 15b (Inventive) (0.3 mmol of Ni(0))

1 eq. of NTP was admixed with 300 eq. of 3PN and 2 eq. of ligand 1,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of Al(O-s-Bu)₃and 1 eq. of ZnCl₂ was added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 265 eq. of HCN/h*Ni werethen injected. After 1, 2, 3, 4, 5 and 10 minutes, a sample was takenfrom the reaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

Min 4PN ADN 1 2.7 3.2 2 3.1 5.2 3 3.3 7.8 4 3.4 9.6 5 3.3 11.9 10 2.523.9

Comparative Overview

4PN content [GC percent by weight] Example 14 Example 15a Example 15bTime [min.] No additive With Et₃Al With Al-tri-s-butoxide 1 2.6 1.9 2.72 3 2.2 3.1 3 3.3 2.4 3.3 4 3.3 2.6 3.4 5 3.1 2.6 3.3 10 2.6 1.5 2.5

The inventive additives thus do not exhibit any isomerization activityin the sense of U.S. Pat. No. 4,874,844 within the measurement accuracy.

ADN content [GC percent by weight] Example 14 Example 15a Example 15bTime [min.] No additive With Et₃Al With Al-tri-s-butoxide 1 3.7 3.6 3.22 7.1 4.5 5.2 3 9.8 7.7 7.8 4 12.1 10.9 9.6 5 15.5 11.5 11.9 10 27.225.4 23.9

The inventive additives thus exhibit no influence on the reaction rateof the hydrocyanation in the sense of U.S. Pat. No. 4,874,884 within themeasurement accuracy.

Example 16 (Comparative) (0.29 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 2,stirred at 25° C. and heated to 60° C. 1 eq. of ZnCl₂ was added to thismixture and it was stirred for a further 5 min. In an Ar carrier gasstream, 314 eq. of HCN/h*Ni were then injected. After 50 min., themixture took up no more HCN; a sample was taken from the reactionmixture and the following results were obtained by gas chromatography(GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 1.8 1.5 25.0 94.4

Example 17 (Inventive): (0.29 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 2,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of Et₃Al and 1eq. of ZnCl₂ were added to this mixture and it was stirred for a further5 min. In an Ar carrier gas stream, 340 eq. of HCN/h*Ni were theninjected. After 135 min., the mixture took up no more HCN; a sample wastaken from the reaction mixture and the following results were obtainedby gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 0.5 3.1 70.8 95.8

Example 18 (Comparative) (0.43 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 3,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 297 eq. of HCN/h*Ni were then injected. After 65min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 2.2 3.2 27.0 89.4

Example 19 (Inventive) (0.43 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 3,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of Et₃Al and 1eq. of ZnCl₂ were added to this mixture and it was stirred for a further5 min. In an Ar carrier gas stream, 335 eq. of HCN/h*Ni were theninjected. After 160 min., the mixture took up no more HCN; a sample wastaken from the reaction mixture and the following results were obtainedby gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 0.6 8.5 70.8 89.3

Example 20 (Comparative): (0.22 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 4,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 272 eq. of HCN/h*Ni were then injected. After 30min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN AND ADN selectivity (%) 3.0 1.6 3.3 66.8

Example 21 (Inventive) (0.23 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 2 eq. of ligand 4,stirred at 25° C. for one hour and heated to 60° C. 1 eq. of Et₃Al and 1eq. of ZnCl₂ were added to this mixture and it was stirred for a further5 min. In an Ar carrier gas stream, 298 eq. of HCN/h*Ni were theninjected. After 100 min., the mixture took up no more HCN; a sample wastaken from the reaction mixture and the following results were obtainedby gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 2.5 4.3 41.0 90.5

Example 22 (Comparative) (0.4 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 3 eq. of ligand 5,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 337 eq. of HCN/h*Ni were then injected. After 150min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 0.7 4.7 72.4 94.0

Example 23 (Inventive) (0.4 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 3 eq. of ligand 5,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of Al(O-s-Bu)₃and 1 eq. of ZnCl₂ were added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 299 eq. of HCN/h*Ni werethen injected. After 195 min., the mixture took up no more HCN; a samplewas taken from the reaction mixture and the following results wereobtained by gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 0 4.9 90.9 94.7

Example 24 (Comparative): (0.4 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 3 eq. of ligand 6,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of ZnCl₂ wasadded to this mixture and it was stirred for a further 5 min. In an Arcarrier gas stream, 313 eq. of HCN/h*Ni were then injected. After 95min., the mixture took up no more HCN; a sample was taken from thereaction mixture and the following results were obtained by gaschromatography (GC percent by weight, internal standard: ethylbenzene):

4PN MGN ADN ADN selectivity (%) 2.0 2.7 31.4 92.1

Example 25 (Inventive) (0.4 mmol of Ni(0))

1 eq. of NTP was admixed with 1000 eq. of 3PN and 3 eq. of ligand 6,stirred at 25° C. for one hour and heated to 70° C. 1 eq. of Al(O-s-Bu)₃and 1 eq. of ZnCl₂ were added to this mixture and it was stirred for afurther 5 min. In an Ar carrier gas stream, 303 eq. of HCN/h*Ni werethen injected. After 130 min., the mixture took up no more HCN; a samplewas taken from the reaction mixture and the following results wereobtained by gas chromatography (GC percent by weight, internal standard:ethylbenzene):

4PN MGN AND ADN selectivity (%) 0 4.1 74.6 94.8

Example 26 (Comparative)

The procedure of example 14 was repeated with the difference that amixture of 30 eq. of 4PN and 270 eq. of 3PN was used at the start. Asample was taken from the reaction mixture after 1, 2, 3, 4, 5 and 10minutes and the content of 4PN was determined by gas chromatography (GCpercent by weight, internal standard: ethylbenzene) to determine theinfluence on the reaction rate of the hydrocyanation to the ADN of theinventive additives and the following results were obtained:

Min 4PN ADN 1 3.4 4.1 2 3.4 5.7 3 3.3 7.4 4 3.4 10 5 3.4 12.1 10 3 24.5

Example 27 (Inventive)

The procedure of example 15 was repeated with the difference that amixture of 30 eq. of 4PN and 270 eq. of 3PN was used at the start. Asample was taken from the reaction mixture after 1, 2, 3, 4, 5 and 10minutes and the content of 4PN was determined by gas chromatography (GCpercent by weight, internal standard: ethylbenzene) to determine theinfluence on the reaction rate of the hydrocyanation to give ADN of theinventive additives and the following results were obtained:

Min 4PN ADN 1 3.2 3.5 2 3.2 4.7 3 3.3 7.2 4 2.9 8.9 5 2.7 14.1 10 2.226.5

Comparative Overview

4PN content [GC percent by weight] Example 26 Example 27 Time [min.]Without additive With Et₃Al 1 3.4 3.2 2 3.4 3.2 3 3.3 3.3 4 3.4 2.9 53.4 2.7 10 3 2.2

The inventive additives thus do not exhibit any isomerization activityin the sense of U.S. Pat. No. 4,874,884 within the measurement accuracy.

ADN content [GC percent by weight] Example 26 Example 27 Time [min.]Without additive With Et₃Al 1 4.1 3.5 2 5.7 4.7 3 7.4 7.2 4 10 8.9 512.1 14.1 10 24.5 26.5

The inventive additives thus do not exhibit any influence on thereaction rate of the hydrocyanation in the sense of U.S. Pat. No.4,874,884 within the measurement accuracy.

1. A system which is suitable as a catalyst for the hydrocyanation ofolefinically unsaturated compounds and comprises; a) Ni(0), b) acompound which complexes Ni(0) as a ligand and comprises phosphites,phosphonites or mixtures thereof, c) a Lewis acid and d) a compound ofthe formula M R_(n), where c) and d) are different, and where M isselected from Al or Ti, R is selected from identical or differentmonovalent alkoxy radicals, in which the alkoxy radicals may be bondedtogether, and if M=Al, R may also be identical or different monovalentalkyl radicals, in which the alkyl radicals may be bonded together orone or more alkyl radicals may be bonded to one or more of theabovementioned alkoxy radicals, and n is the valency of M.
 2. The systemaccording to claim 1, wherein R, is an alkoxy radical selected from thegroup consisting of, methoxy, ethoxy, 1-propoxy, 2-propoxy, 1-n-butoxy,2-n-butoxy, 1-isobutoxy and 2-isobutoxy.
 3. The system according toclaim 1, wherein R is an alkyl radical, selected from the groupconsisting of methyl, ethyl, 1-propyl, 2-propyl, 1-n-butyl, 2-n-butyl,1-isobutyl or 2-isobutyl.
 4. The system according to claim 1, whereincompound d) is a titanium tetraalkoxide.
 5. The system according toclaim 1, wherein compound d) is an aluminum trialkoxide.
 6. The systemaccording to claim 1, wherein compound d) is a trialkylaluminum.
 7. Thesystem according to claim 1, wherein the R radicals in compound d) arethe same.
 8. A process for hydrocyanating an olefinically unsaturatedcompound comprising contacting the olefinically unsaturated compoundwith the catalyst system, according to claim
 1. 9. The process accordingto claim 8, wherein the olefinically unsaturated compound comprises afunctional group selected from the group consisting of —CN, —COOR¹, and—CONR²R³ where R¹, R², R³ are each independently the same or different,H or alkyl.
 10. The process according to claim 8, wherein theolefinically unsaturated compound used is a compound of the formula(C₄H₇)—X where X is functional group selected from the group consistingof —CN, —COOR¹, and —CONR²R³ where R¹, R², R³ are each independently,the same or different, H or alkyl.
 11. The process according to claim 8,wherein the olefinically unsaturated compound used is a linearpentenenitrile.
 12. The process according to 8, wherein the olefinicallyunsaturated compound used is 3-pentenenitrile or 4-pentenenitrile. 13.The catalyst system of claim 1 wherein the zero-valent nickel complexcomprises a ligand of formula IP(X¹R¹)(X²R²)(X³R³)  I wherein X¹, X² and X³ are each independentlyoxygen or a single band, and R¹, R² and R³ are each independently alkylradicals having from 1 to 10 carbon atoms or an aryl group.
 14. Thecatalyst system of claim 13 wherein R¹, R² and R³ are each independentlyselected from the group consisting of phenyl, o-tolyl, m-tolyl andp-tolyl.